Key receivable in a T-groove of a support

ABSTRACT

A key is receivable in a T-groove of a support for securing an object to the latter. The key has an elongated body provided with two spaced parallel end faces extending transversely to the longitudinal axis of the body, a pair of side faces each of which includes a first side face portion extending longitudinally of the body from one of the end faces part of the distance towards the other end face, and a second side face portion extending from the respective first side face portion to the other end face. The first side face portions extend parallel to the longitudinal axis and are transversely spaced by a distance smaller than the narrowest dimension of a T-groove into which the body is to be inserted, and the second side face portions are inclined from the respective first side portions in direction towards the longitudinal axis. An upper face of the body has in the region of the end faces respective upper face portions which are located at opposite sides of the longitudinal axis and which are adapted to engage from below the respective opposite shoulders bounding the narrowest dimension of the T-groove. A screw or similar arresting device is provided for arresting the body in the T-groove.

United States Patent lLetzel et al.

1 1 Mall. 25, 1975 KEY RECEIVABLE IN A T-GROOVE OF A SUPPORT Inventors: ll-ielmut Letzel, Cologne; Wolfgang Letzel, Porz-Eil, both of Germany Assignee: Jakob Wollenhaupt Werkmittel, K.

G., Cologne-Holweide, Germany Filed: June 6, 1974 Appl. No.: 477,088

Foreign Application Priority Data June 9, 1973 Germany i. 2329640 References Cited UNITED STATES PATENTS 2/1945 Jesionowski 308/3 A X 11/1958 Elsner i. l5l/4li7l UX 10/1968 Kane et a]...

8/1969 Hohwart 279/123 Primary E,\'un1inerWerner H. Schroeder Assistant E,\'un1inw'Wayne L. Shedd Attorney, Agent, or Firm-Michael S. Striker [57] ABSTRACT A key is receivable in a T-groove of a support for securing an object to the latter. The key has an elongated body provided with two spaced parallel end faces extending transversely to the longitudinal axis of the body, a pair of side faces each of which includes a first side face portion extending longitudinally of the body from one of the end faces part of the distance towards the other end face, and a second side face portion extending from the respective first side face portion to the other end face. The first side face portions extend parallel to the longitudinal axis and are transversely spaced by a distance smaller than the narrowest dimension ofa T-groove into which the body is to be inserted, and the second side face portions are inclined from the respective first side portions in direction towards the longitudinal axis. An upper face of the body has in the region of the end faces respective upper face portions which are located at opposite sides of the longitudinal axis and which are adapted to engage from below the respective opposite shoulders bounding the narrowest dimension of the T-groove. A screw or similar arresting device is provided for arresting the body in the T-groove.

9 Claims, 17 Drawing Figures PATENTED HARZ 5 I975 SHEET 3 OF 5 PATENTEUMRZSIBYEI 3,873 ,224 sum 5 pg 5 KEY RECEIVABLE IN A T-GROOVE OF A SUPPORT BACKGROUND OF THE INVENTION The present invention relates generally to a key that is receivable in an undercut groove, and more particularly to a key that is receivable in a T-groove of a support for securing an object to the latter.

Keys of this type may, for instance, serve to secure cams or other elements to a support in such a manner that the cams can be moved to different locations on the support or can be removed. They are insertable into the T-groove and can be slid along the same to a desired location. They are usually provided with a screw or the like that is threaded into a bore which extends downwardly from the upper face of the key at an angle, so that the screw itself extends at an angle and the upper portion of the screw extends out of the T-groove through the narrowest slot-shaped part of the same. When the screw is inserted through a part of an object that is to be secured on the support, and is then tightened, it draws the object downwardly against the surface of the support in which the T-groove is formed, and draws the key upwardly until it is firmly held against the underside of the shoulders bounding the slot-shaped part of the T-groove, thus arresting both the key and the object. Keys of this type are used for a variety of purposes in addition to those mentioned above, including the securing of workpieces, the securing of machine components and the like.

Other types of keys of this general characteristic have bores which extend vertically from the upper face, so that the screw itselfis also vertically oriented. The type having the screw that is oriented at an angle of inclination is disclosed in German Pat. No. 1,289,570.

Most of these keys can be inserted only from one end of a T-groove, or else into an enlarged portion of the T-groove which may be provided intermediate the ends of the same. Since this is inconvenient in certain instances, keys have also been developed which can be inserted from above through the narrow slot-shaped part ofa T-groove, rather than having to be slid in from the end of the latter. These keys must evidently have an overall width that is at least slightly smaller than the slot-shaped part of the T-groove in order to be able inserted through the same, and once they are inserted they are angularly displaced in the inner and wider part of the T-groove transversely to the elongation of the latter, so that they engage beneath the opposite shoulders bounding the narrow slot-shaped part of the groove and are then upwardly drawn against the shoulders when the screw is tightened. This type of key is disclosed in German Pat. No. 1,271,492 and is satisfactory in operation except that it has a very specialized and relatively complicated configuration and is therefore rather expensive to produce.

One problem has not heretofore been solved in the prior art: that is to provide a key that can be inserted into a T-groove from above, i.e., through the narrowest slot-shaped portion of the groove, and can also be provided in its upper surface with a bore that is inclined longitudinally of the key and of the groove so that the screw that cooperates with the key can be similarly inclined.

This is a rather important consideration in modern applications because the combination of these features is desirable for securing control cams for program controls, on supports having T-grooves. Quite frequently, programs which must be controlled by means of cams require that 20 or more such cams be secured on a support, and equally frequently, changes must be made in the positioning of the cams (to thereby obtain a change in the operation of the program) the necessity for which becomes apparent only after the program has been undergoing some actual testing. This means that the cams must be readily movable from one position in a T-groove to another and perhaps even be taken out of one of the T-grooves and inserted into a different one. Also, cams must frequently be added in addition to those which are already in place. This means that if the prior-art keys are used, the keys holding the already properly positioned cams of a particular groove to which a further cam is to be added, or wherein one of the cams is to be shifted, must all be loosened and removed in order to permit shifting of the particular cam that requires repositioning or to permit the insertion or removal of a key with its associated cam. Evidently, this is undesirable for reasons which require no explanation. The alternative is to use the specialty key disclosed in German Pat. No. 1,231,492 which, however, is complicated and therefore rather expensive to produce as has been mentioned earlier.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an improved key which is receivable in a T- groove of a support and which avoids the disadvantages of the prior art.

More particularly, it is an object ofthe present invention to provide such an improved key which can be inserted directly from above into a T-groove through the narrowest slot-shaped portion of the same, and which is provided with a mounting screw that extends at an angle to the upper surface of the key and to the elongation of the groove.

In keeping with the above objects, and with others which will become apparent hereafter, one feature of the invention resides accordingly,.in a key receivable in a T-groove of a support for securing an object to the latter, comprising an elongated body having a longitudinal axis and two spaced parallel e'nd faces extending transversely to this axis. A pair of side faces are provided, each including a first side face portion extending longitudinally of the body from one of the end faces part of the distane toward the other end face, and a sec ond side face portion extending from the first side face portion'to the other end face. The first side face portions extend parallel to the longitudinal axis and are transversely spaced from one another by a distance smaller than the narrowest dimension of the T-groove into which the body is to be inserted. The second side face portions are inclined from the respective first side face portions in direction towards the longitudinal axis. An upper face of the body has in the region of the end faces respective upper face portions which are located at opposite sides of the longitudinal axis and which are adapted to engage from below the respective opposite shoulders bounding the narrowest dimension of the T- groove. Arresting means is provided for arresting the body in this T-groove.

In view of the particular configuration of the novel key this arresting means can be in form of a screw that can be threaded into the key at an angle to the upper surface thereof and to the longitudinal direction of the T-groove. Such a key can be inserted from above directly into a T-groove through the narrowest slotshaped portion of the same intermediate already properly positioned keys and their associated cams, without having to shift the same in any way.

According to one embodiment of the invention, the body may have the configuration of an elongated polygon having a hexagonal outline, wherein imaginary lines connecting the opposite corners of the upper face are inclined and wherein the upper face is provided with a trapezoidal shaped upwardly extending projection, as will be discussed in more detail subsequently.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a perspective view illustrating one embodiment of the invention;

FIG. 2 is a side view, showing the key of FIG. 1 in a T-groove, and holding a cam in place on the support in which the T-groove is formed;

FIG. 3 is an end view as seen in the direction of the arrow A, of FIG. 2;

FIG. 4 is a perspective view of FIG. 2;

FIG. 5 is a perspective view showing the key of FIGS. 2 and 4 about to be inserted into a T-groove;

FIG. 6 is a section taken on line aa of FIG. 5;

FIG. 7 is an end view showing a key according to a further embodiment being inserted into a T-groove;

FIG. 8 showing the key in FIG. 7 after it has been tilted into the T-groove;

FIG. 9 is a perspective side view showing the key of FIGS. 7 and 8 during its insertion into the T-groove;

FIG. 10 is a perspective side view of the key in FIG. 9, but showing it in the position which it assumes when it has been tilted as illustrated in FIG. 8;

FIG. 11 is a top plan view of FIG. 9;

FIG. 12 is a top-plan view of FIG. 10; and

FIGS. 13 17 are diagrammatic views to illustrate how the abutment faces on the key of FIGS. 7 12 can be calculated and configurated.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Coming now to a discussion of the drawing in detail, and referring firstly to the embodiment which is illustrated in several views in the FIGS. 1 6, it should be understood that in these Figures and in other Figures the novel key 1 according to the present invention is always of elongated configuration. For purposes of orientation a longitudinal axis LA has been diagrammatically illustrated in FIG. 1; it will be understood that this axis will be aligned with the elongation of a T- groove 4 (see FIGS. 2 6) when the key 1 is being inserted into the latter.

The key 1 in FIGS. 1 6 is configurated as an elongated polygon having a hexagonal outline. It has two axial end faces 6a and 6b which extend parallel to one another and normal to the axis LA. The key 1 also has two side faces, of which one is visible in FIG. 1. This side face is composed of a first side face portion 5a which extends from the end face 6a part of the distance towards the end face 6b, and from which a second side face portion la extends to this other end face 6b. A similar side face lb at the opposite side of the key I is composed of the side face portions 5b and lb, respectively. A comparison of the several FIGS. 1 6 indicates that the side face portions 5a and 5b extend in parallelism with one another, and also parallel to the longitudinal axis LA of the key 1, whereas the side face portions 1a and lb are inwardly inclined towards the axis LA and towards that end face 6a or 6b which is remote from the respective side face portion 5a or 5b. The side face portions 50 and 5b will, when the key 1 is inserted into a T-groove 4 and has been turned to the final mounting position, abut the groove walls 4a and 4b of the groove, as shown in FIG. 3. In this position the longitudinal axis LA of the key 1 will no longer extend lengthwise of the groove 4, but will be inclined to the elongation thereof.

The key also has an upper face 2a which is provided in the region of one end of the key 1, here in the region of the end face 6b, with an upwardly extending projection 7 that in this embodiment has substantially trapezoidal configuration. One surface 7a of the projection 7 is located in the plane of and merges with the side face portion 1a; the surface 7b which is located opposite the surface 7a but is not parallel to the latter, forms with a part of the upper face 2a a step 8. The surfaces 7b and 7c of the projection 7a are parallel to one another, and the surface 7b is located in the plane of and merges with the end face 6b. The upper face 2a of the key 1 is formed with a tapped bore which is inclined longitudinally of the key 1 and which extends into (and, in this particular embodiment, all the way through) the key 1 so that a screw 13 can be threaded into this bore at a similar inclination, as shown in FIG. 1. A bevel 2b extends from the respective end faces and side faces to the (not visible) under face of the key 1.

FIG. 2 shows an object, here illustrated as a cam for operating a program switch or the like and identified with reference numeral 9 to be connected with the key 1 by means of the screw 13. For'this purpose the object 9 is formed with an inclined bore through which the screw 13 extends, so that the screw has its head located in a position in which it is always accessible for engagement with a screw driver or similar tool. The key 1 in FIG. 2 is received in the groove 4 of a support 1, both being shown only diagrammatically in chain lines, and the cam 9 is urged against the upper surface of the support 21 whereas the key 1 is drawn from below against the underside of the shoulders 40 and 4d bounding the groove 4 (compare FIG. 3) so that both the key 1 and the cam 9 are firmly held in place on the support 21. The cam 9 is formed on its underside with a guide projection 9a which engages into the narrowest slotshaped portion of the T-groove 4, and the projection 7 engages into a recess 9b formed for this purpose in the guide projection 9a, to further preclude any relative displacement of the cam 9 and the key 1.

FIG. 3 shows most clearly how in the mounted condition of the cam 9 and the key 1, the step 8 of the key 1 engages beneath the shoulder 40 of the T-groove 4, and how a portion of the upper face 2a engages beneath the opposite shoulder 4d at a location that is longitudinally spaced from the step 8.

FIG. 4 illustrates how, once the key 1 has been inserted through the narrowest slot-shaped portion of the T-groove 1, and is tilted transversely of the elongation of the latter, a portion of its surface 2a in the region of the side face portion lb and in the region of the side face portion 5b engages beneath the shoulder 4d of the groove 4, and FIG. 5 makes it clear that during the initial insertion the cam 9a will be inclined with reference to the upper surface 21a of the support 21 in which the groove 4 is formed, whereas when cam 9 and key 1 are fixedly mounted in the groove 4 as shown in FIG. 4, the cam 1 will have a vertical orientation with respect to this upper surface 21a.

To utilize the key of FIGS. 1 6, the key is inserted from above into the narrowest slot-shaped portion 3 of the T-groove 4 until the abutment face of the guide portion 9a of the cam 9 (which is already connected with the key by means of the screw 13) contacts the upper surface 21a of the support 21. At this time, the cam 9 will have been moved by engagement with the upper surface 21a from its inclined position of FIG. 5 to its vertical position of FIG. 4. The screw 13 is now turned to tighten it, and this causes initially a tilting or pivoting of the key I transversely of the elongation of the groove 4, but within the latter, until the side face portions 5a and 5b abut the side walls 40 and 4b, respectively. As soon as the step 8 moves against the shoulder 40 of the groove 4, the opposite axial end of the key 1 abuts the inner groove wall 4a, and further turning of the screw in a sense tightening the latter now causes the key 1 to be drawn upwardly against the shoulders 4c and 4d, and at the same time casues the cum 9 to be drawn downwardly against the upper surface 21a of the support 21 until both elements are tightly secured to the support 21.

The key 1 described with respect to FIGS. 1- 6 needs the objects which have been outlined earlier herein. However, it must be inserted into the groove 4 while being inclined at an angle to the upper surface 21a of the support 21. This can be disadvantageous in some respects, and in particular ifan object such as a cam 9 must be secured to the support 21 which is relatively long and therefore requires not a single key but two or more which are spaced longitudinally of the groove 4. In such a case the necessity to have both keys properly oriented at an angle to the upper surface 210 of the support 21, while inserting them simultaneously into the groove 4 at spaced locations of the latter, would make the use of the invention unnecessarily difficult. In situations where a single object to be fastened to the support 21 requires the use of two or more of the keys, it is, therefore, desirable that it be possible to in-.

sert these keys in vertical orientation intothe groove 4 rather than requiring them to be inclined to the uppersurface 21a.

This is made possible by the embodiment which is described with respect to FIGS. 7 12 and wherein like reference numerals identify like components as before. In FIGS. 7 12, however, the key 1 is provided with surface portions 22a and 22b at opposite ends of the key 1 for engagement with the shoulders 4c and 4d of the groove 4. These surface portions are produced by removing material from the upper face 2a in vertical direction and in a direction which is inclined thereto and inwardly of the face portions 5a and 5b. The heights I1 and 11 of the vertical edge faces which are thus formed and the widths in and (compare FIG. 17 which will be explained later) must be so selected that the key 1 can be inserted in vertical orientation into the groove 4, and the inclination between the edge faces produced by the vertical material removal and the abutment faces 22a, 22b must be so selected that these abutment faces, after tilting the'key 1 through the angle or (compare FIG. 15 which will be explained later) which is dictated by the dimensions of the T-groove 4, will engage from below against the shoulders 4c and 4d in such a manner that they can be drawn against them and fix the key in place.

FIG. 7 shows how this key is inserted from above into the groove 4 and how it is vertically oriented with respect to the upper surface 21a ofthe support 21 at this time. FIG. 8 shows how the key has been tilted transversely of the elongation of the groove 4, and how the abutment faces 22a and 22b engage from below the shoulders 40 and 4d when the screw 13 is turned to draw the cam 9 downwardly against the upper surface 210 and to draw the key 1 upwardly against the undersides of the shoulders 40 and 4d. This Figure also shows how at the intersection of the surface portions 512 and 1b a flattened facet is formed, by removing material in the region which is shown in chain lines and indicated by reference numeral 18; thepurpose of this is to prevent the edge which would otherwise be formed at this intersection from interfering with the engagement of the abutment faces 22a and 2bb with the shoulders 4c and 4d, respectively.

FIG. 9 illustrates in a perspective view the position which the key 1 assumes as it is being inserted from above into the groove 4; in other words, FIG. 9 shows in perspective the same position of the key 1 that has been illustrated in an end view in FIG. 7. Similarly, FIG. 10 shows in perspective view the same position which has been illustrated for the key 1 in an endview in FIG. 8.

FIG. 11 shows the position of the key 1 (the cam 9 has been omitted in this view) in a top-plan view, corresponding to the views of FIGS. 7 and 9, whereas FIG.

12 is a top plan view (again with the cam 9 omitted) corresponding to the positions shown in FIGS. 8 and 10.

In FIGS. 13 17 it is diagrammatically shown how the shaping of the abutment faces 22a and 22b can be calculated. The key 1 is to be insertable in a vertical orientation from above into the groove 4, and to thereafter so tilted that the abutment 22a and 22b (which are still to be calculated) engage beneath the shoulders 4c and 4d. Tilting takes place through an angle oz which is to be determined in respect of the dimensions of the groove 4, so that the angle a constitutes a fixed predetermined value.

During this tilting, the portion of the key 1 located forwardly of the screw 13 will move downwardly whereas the portion located behind the screw will move upwardly. The material removal from the upper face of the key 11 must therefore be so calculated that the abutment faces 22a and 22b produced by such material removal compensate for the difference between the upward and downward movement of the opposite end portions of the key, so that after the tilting is completed the abutment faces 22a and 22b engage from beneath the shoulders 4c and 4d which extend horizontally; in other words, the abutment faces 22a and 22b must themselves extend horizontally or nearly so.

FIGS. 13 17 illustrate the path traversed by the corners at the upper edge ofthe end face 6a during the tilt-- ing movement. For reasons of simplicity FIG. 3 shows the key 1 merely of rectangular outline, having the screw 13 threaded into it.

FIG. 14 is a top-plan view of the key 1, with the screw 13 being omitted, and FIG. 15 is a top-plan view as seen in the direction of elongation of the longitudinal axis of the screw 13. FIG. 16 is a side view of the key 1 and FIG. 17 finally illustrates the position and configuration of the abutment faces 22a and 22b.

The corners at the upper edge of the end face 6a are identified with reference characters A and B in FIG. 13, and their position A and B after tilting, that is after they have moved in the plane E-E' during tilting, has been shown in FIG. 13. The drawing also shows how the positions A and B can be graphically transferred to the illustration in FIG. 16, where they are indicated with reference characters A and B". When the same is done for all other corners of the key 1, then the orientation of the key 1 in the final tilted position can be graphically shown, as has been done in chain lines in FIG. 16.

FIG. 17, finally, indicates by the horizontal chain line E"-E" the plane into which the abutment faces 22a and 22b must be moved at the end of the tilting move ment in order for them to engage the undersides of the grooves 40 and 4d. The positions A and B have been calculated as explained before, and the plane E"E" must pass through the end face 6a. This is shown at the left-hand end side of FIG. 17, wheres the right-hand side the outline of the opposite end face 6b is shown. The width b and b for the abutment faces 22a and 22b are then calculated in dependence upon the width of the shoulders 4c and 4d, respectively.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of constructions differing from the types describes above.

While the invention has been illustrated and described as embodied in a key which is receivable in a T-groove of a support, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims.

1. A key receivable in a T-groove of a support for securing an object to the latter, comprising an elongated body having a longitudinal axis and two spaced parallel end faces extending transversely to said axis, a pair of side faces each including a first side face portion extending longitudinally of said body from one ofsaid end faces part of the distance towards the other end face and a second side face portion extending from said first side face portion to said other end face, said first side face portions extending parallel to said longitudinal axis and being transversely spaced by a distance smaller than the narrowest dimension of a T-groove into which said body is to be inserted, and said second side face portion being inclined from the respective first side face portions in direction towards said longitudinal axis, and an upper face having in the region of said end faces respective upper face portions which are located at opposite sides of said longitudinal axis and which are adapted to engage from below the respective opposite shoulders bounding said narrowest dimension of said T-groove; and arresting means for arresting said body in said T-groove.

2. A key as defined in claim 1, wherein said body comprises in the region of said one end face a projection extending upwardly from said upper face and which has two parallel first surfaces extending transverse to said axis and one of which is located in the plane of and merges with said one end face, and a pair of non-parallel second surfaces one of which is located in the plane of and merges with one of said second side face portions and the other of which extends parallel to said first side face portions.

3. A key as defined in claim 2, wherein said projection is of substantially trapezoidal shape.

4. A key as defined in claim 2, wherein said body rcsembles an elongated polygon having a hexagonal outline.

5. A key as defined in claim 2, wherein one of said upper face portions forms with said other second surface a step in which one of said opposite shoulders is receivable.

6. A key as defined in claim 1, wherein said body also has a lower face; and a bevel extending from said lower face to the respective side faces and end faces.

7. A key as defined in claim 1, wherein each of said upper face portions is recessed in said upper face and bounded by a first edge face extending normal to the plane of said upper face and a second edge face extending from said first edge to the respectively adjacent first side face portion.

8. A key as defined in claim 7, wherein the respectively associated first and second edge faces are mutually inclined and so oriented relative to said longitudinal axis that a respective one of said shoulders of said T-groove can matingly engage them when said body is angularly displaced in said T-groove transverse to the elongation of the latter.

9. A key as defined in claim 1, wherein the associated first and second side face portions intersect one another at a line of intersection, and wherein the respective side face is formed with a flattened facet at said line of intersection, which is recessed inwardly towards said longitudinal axis. 

1. A key receivable in a T-groove of a support for securing an object to the latter, comprising an elongated body having a longitudinal axis and two spaced parallel end faces extending transversely to said axis, a pair of side faces each including a first side face portion extending longitudinally of said body from one of said end faces part of the distance towards the other end face and a second side face portion extending from said first side face portion to said other end face, said first side face portions extending parallel to said longitudinal axis and being transversely spaced by a distance smaller than the narrowest dimension of a T-groove into which said body is to be inserted, and said second side face portion being inclined from the respective first side face portions in direction towards said longitudinal axis, and an upper face having in the region of said end faces respective upper face portions which are located at opposite sides of said longitudinal axis and which are adapted to engage from below the respective opposite shoulders bounding said narrowest dimension of said T-groove; and arresting means for arresting said body in said T-groove.
 2. A key as defined in claim 1, wherein said body comprises in the region of said one end face a projection extending upwardly from said upper face and which has two parallel first surfaces extending transverse to said axis and one of which is located in the plane of and merges with said one end face, and a pair of non-parallel second surfaces one of which is located in the plane of and merges with one of said second side face portions and the other of which extends parallel to said first side face portions.
 3. A key as defined in claim 2, wherein said projection is of substantially tRapezoidal shape.
 4. A key as defined in claim 2, wherein said body resembles an elongated polygon having a hexagonal outline.
 5. A key as defined in claim 2, wherein one of said upper face portions forms with said other second surface a step in which one of said opposite shoulders is receivable.
 6. A key as defined in claim 1, wherein said body also has a lower face; and a bevel extending from said lower face to the respective side faces and end faces.
 7. A key as defined in claim 1, wherein each of said upper face portions is recessed in said upper face and bounded by a first edge face extending normal to the plane of said upper face and a second edge face extending from said first edge to the respectively adjacent first side face portion.
 8. A key as defined in claim 7, wherein the respectively associated first and second edge faces are mutually inclined and so oriented relative to said longitudinal axis that a respective one of said shoulders of said T-groove can matingly engage them when said body is angularly displaced in said T-groove transverse to the elongation of the latter.
 9. A key as defined in claim 1, wherein the associated first and second side face portions intersect one another at a line of intersection, and wherein the respective side face is formed with a flattened facet at said line of intersection, which is recessed inwardly towards said longitudinal axis. 